A valve timing control device operates in synchronization with a crankshaft and a camshaft of an engine, which is an internal combustion engine. A relative rotational phase of the valve timing control device can be changed or set by control of the relative rotational position between an advanced angle chamber and a retarded angle chamber, which are provided between the driven side rotational member and the driving side rotational member respectively. Then, a preferable operating state can be attained by properly setting the relative rotational phase in response to an operating state of the engine.
A hydraulic pump supplies and discharges an operational fluid to fluid pressure chambers of the valve timing control device and is driven by the crankshaft of the engine. Thus, while the engine is driven, the operational fluid is supplied into the fluid pressure chambers by the hydraulic pump. Thus, the control of the relative rotational position is performed smoothly.
On the other hand, while the engine is stopped, the hydraulic pump is not driven, and thus the operational fluid flows out from the fluid pressure chambers by its own weight.
Therefore, the operational fluid is reserved in an oil pan, and the temperature of the oil is low at the start of the engine. In this state, viscosity of the operational fluid is high, and resistance of the flow passage is large. Consequently, it is time-consuming to supply the operational fluid to the fluid pressure chambers via an oil passage of an oil pressure circuit. For the reason, it is difficult to smoothly control the relative rotational position of the driven side rotational member relative to the driving side rotational member and properly control the opening and closing timing of an intake valve immediately after the start of the engine.
In JP 2003-278566A, a technology, which intends to control the valve timing control device properly at the start of the engine, is disclosed. A configuration which supplies the operational fluid during engine stopping to prevent the operational fluid from flowing out from the fluid pressure chambers of the valve timing control device while the engine is temporary stopped. This allows the valve timing control device to properly control the opening and closing timings of the intake valve at the start of the engine.
According to JP 2003-278566A, in addition to the hydraulic pump, an extra pump is required to supply the operational fluid during the engine stopping. Consequently, the configuration of the valve timing control device becomes complicated, and weight of the vehicle is increased.
A certain amount of time has elapsed since the engine started, then the viscosity of the operational fluid becomes high and it is not possible to supply the operational fluid to a desired area promptly. In order to lower the viscosity of the operational fluid, it is necessary to raise the temperature, however it needs a certain amount of time.
The present invention has been made in view of the above circumstances, and provides a valve timing control device which is able to supply the high viscosity operational fluid in a short time and perform the opening and closing timing control of the valves at a proper timing with a simple configuration.